This invention relates to computer monitors and, more particularly, to a single horizontal scan range cathode ray tube (CRT) monitor for use with personal computers having differing output display signal formats.
There is little standardization among personal computer (PC) manufacturers for the resolution and frequency of the display signals generated by the display cards of the PCs. On the other hand, it is generally more expensive and complicated to make analog monitors which can adapt to a plurality of display signal frequencies. One such possible arrangement is shown in FIG. 1. In this arrangement a PC 10 includes a display card (not shown) having a digital to analog (D/A) converter 12 to output analog display signals, at a frequency and resolution set by the PC, to a CRT multiple scanning frequency monitor 14. The monitor 14 has to detect the frequency and adjust its scanning frequency to match that of the initial display signals. Such a monitor is complex and expensive to build.
Still another possible monitor display arrangement is illustrated in FIG. 2. Again the PC 10 includes a display card (not shown) having a digital to analog (D/A) converter 12 to output analog display signals, at a frequency and resolution set by the PC, to a single scan frequency liquid crystal display (LCD) monitor 16.
The LCD monitor 16 includes an A/D converter 18 that converts the received analog signals into digital signals. A scaling engine 20 within the LCD monitor 16 converts the digital display signals into a frequency and resolution that are compatible with the LCD monitor 16 and supplies them to a display circuit (not shown) within the LCD monitor 16. In this arrangement, the A/D converter and the LCD panel are expensive.
Yet another possible arrangement is illustrated in FIG. 3. In this arrangement the PC 10 includes a display card (not shown) having a digital to analog (D/A) converter 12 to output analog display signals, at a frequency and resolution set by the PC, to an A/D converter 24 of a single scan CRT monitor 22. The output of the A/D converter 24 is supplied to a scaling engine 26 that converts the digital display signals into a frequency and resolution that are compatible with the CRT monitor 22 and supplies them to a D/A converter 28. The analog output display signals of the D/A converter 28 are supplied to the monitor 22 for display at a resolution and frequency compatible with the monitor. The disadvantages of this arrangement are also that it is complex to manufacture and expensive.
Lastly, in the possible arrangement of FIG. 4, a PC 30 having an internal scaling engine 32 outputs digital display signals at a resolution and frequency compatible with a single scan LCD monitor 16. While this arrangement has the advantage of a lower cost host, the LCD panel is still expensive for general use, e.g. in desktop PCs.
What is needed is a single horizontal scan range monitor, preferably a CRT monitor, that is inexpensive, not complex to make, and allows the monitor to be compatible with PCs having display circuits that output display signals at a variety of different scanning frequencies and display resolutions.